The work is in progress for immunoglobulins. The number and nature of receptor sites for human IgG Fc fragment is being determined. The function of IgG Fc receptor will be investigated to determine the mechanism by which attachment of immune complexes to the receptor triggers release reaction from human platelets. A second major line of investigation will be determination of the nature of receptor for endotoxin in human platelets and its relationship to other known receptors on human platelets. The mechanism of human platelet membrane changes upon interaction of endotoxin with membrane receptor will be examined. A third line of investigation will encompass a series of experiments on the function of human platelets under conditions affecting acid-base balance due to respiratory and metabolic factors. BIBLIOGRAPHIC REFERENCES: Des Prez, R.M., Bryan, C.S., Hawiger, J., and Colley, D.G.: The function of the classical and alternate pathways of human complement in serum treated with EGTA and MgEGTA. Infection and Immunity. 11: 1235-1243, 1975; Marney, S.R., Jr., Colley, D.G., and Des Prez, R.M.: Alternate complement pathway induction of aggregation and release of 5HT and ADP by rabbit platelets. J. Immunol. 114:696-703, 1975.